1. Field of the Invention
This invention is in the field of bicycle brakes, especially rim brakes, including caliper, cantilever, and hydraulic types.
2. Description of Prior Art
Bicycle brakes are of three main types--rim, disc, and drum. Disc brakes have a metal disc attached to the wheel hub, which is clamped between two pads, and thus slowed by the brake. Disc brakes are expensive and heavy. Drum brakes, including coaster brakes, are dissimilar to the present invention.
Rim brakes clamp the wheel rim between two pads. They are lighter than disc brakes, because: 1) they do not require a disc; 2) they have greater braking moment on the wheel, so less pad force is required, allowing lighter parts; and 3) their higher mounting site results in shorter control lines. Since wheel rims are less true than discs, rim brake pads need more clearance to the rim, and therefore longer pad movement than disc brakes, so they need longer actuator parts. Rim brakes also need means to retract the pads enough to admit the tire between them for wheel removal.
Caliper rim brakes, as in U.S. Pat. No. 4,838,387 (Yoshigai), comprise two arms pivoting on a bolt in the velocipede frame centered just above a tire. The arms reach around the tire to hold brake pads at each side of the rim, and clamp them against the rim. These brakes cannot provide maximum firmness, due to flex in the arms. This is especially so with wide tires, which require longer arms. The pads wear unevenly, due to the flex and arc of the arms.
Cantilever rim brakes, as in U.S. Pat. No. 4,768,623 (Nagano), comprise two levers, each bolted to a pivot mount on the fork on each side of the rim. The main brake cable is connected by a bridge to a straddle cable, which effectively branches the main cable into two ends, each connected to the upper end of one of the levers. The pad moves in an arc, causing uneven, accelerated wear. These brakes are highly inconvenient to adjust, and must be readjusted for toe, alignment, and vertical position as the pads wear and after each pad replacement. A limit on the firmness of these brakes is flex in the fork. The cantilever mount is positioned below the level of the rim. The fork bows outward noticeably under braking stress at this point.
Hydraulic piston brakes are powerful, firm, and linear, but are also heavy, expensive, and require maintenance of hydraulic fluid. The present invention is a cable-operated piston brake with the advantages of hydraulic piston brakes, and without the above disadvantages. It provides features for increased power, convenience of installation, adjustment, and wheel removal.
French patents 56,689 (Durif) and 943,589 (Fonteneau) show cable-operated piston rim brakes. They do not route the cable parallel to the piston on both sides it for maximum power and symmetric cable force on the piston. The actuator cable pulls the end of the piston sideways, creating friction. They do not provide enclosed cases. 943,589 provides a case, but It requires a slot in the top for the cable entrance, which allows contaminants to enter the case.